From: Alexei Starovoitov <ast@kernel.org>
Date: Wed, 15 Dec 2021 12:35:34 -0800
Subject: selftest/bpf: Add a test that reads various addresses.
Patch-mainline: v5.16-rc6
Git-commit: 7edc3fcbf9a2b2e3df53c9656a9f85bf807affac
References: jsc#PED-1377

Add a function to bpf_testmod that returns invalid kernel and user addresses.
Then attach an fexit program to that function that tries to read
memory through these addresses.

This logic checks that bpf_probe_read_kernel and BPF_PROBE_MEM logic is sane.

Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Shung-Hsi Yu <shung-hsi.yu@suse.com>
---
 tools/testing/selftests/bpf/bpf_testmod/bpf_testmod.c  |   20 +++++++++++++++++
 tools/testing/selftests/bpf/progs/test_module_attach.c |   12 ++++++++++
 2 files changed, 32 insertions(+)

--- a/tools/testing/selftests/bpf/bpf_testmod/bpf_testmod.c
+++ b/tools/testing/selftests/bpf/bpf_testmod/bpf_testmod.c
@@ -33,6 +33,22 @@ noinline int bpf_testmod_loop_test(int n
 	return sum;
 }
 
+__weak noinline struct file *bpf_testmod_return_ptr(int arg)
+{
+	static struct file f = {};
+
+	switch (arg) {
+	case 1: return (void *)EINVAL;		/* user addr */
+	case 2: return (void *)0xcafe4a11;	/* user addr */
+	case 3: return (void *)-EINVAL;		/* canonical, but invalid */
+	case 4: return (void *)(1ull << 60);	/* non-canonical and invalid */
+	case 5: return (void *)~(1ull << 30);	/* trigger extable */
+	case 6: return &f;			/* valid addr */
+	case 7: return (void *)((long)&f | 1);	/* kernel tricks */
+	default: return NULL;
+	}
+}
+
 noinline ssize_t
 bpf_testmod_test_read(struct file *file, struct kobject *kobj,
 		      struct bin_attribute *bin_attr,
@@ -43,6 +59,10 @@ bpf_testmod_test_read(struct file *file,
 		.off = off,
 		.len = len,
 	};
+	int i = 1;
+
+	while (bpf_testmod_return_ptr(i))
+		i++;
 
 	/* This is always true. Use the check to make sure the compiler
 	 * doesn't remove bpf_testmod_loop_test.
--- a/tools/testing/selftests/bpf/progs/test_module_attach.c
+++ b/tools/testing/selftests/bpf/progs/test_module_attach.c
@@ -87,6 +87,18 @@ int BPF_PROG(handle_fexit,
 	return 0;
 }
 
+SEC("fexit/bpf_testmod_return_ptr")
+int BPF_PROG(handle_fexit_ret, int arg, struct file *ret)
+{
+	long buf = 0;
+
+	bpf_probe_read_kernel(&buf, 8, ret);
+	bpf_probe_read_kernel(&buf, 8, (char *)ret + 256);
+	*(volatile long long *)ret;
+	*(volatile int *)&ret->f_mode;
+	return 0;
+}
+
 __u32 fmod_ret_read_sz = 0;
 
 SEC("fmod_ret/bpf_testmod_test_read")